1. Field of the Invention
The present invention relates to a silicon carbide (SiC) device. Particularly, it relates to an electrode for p-type SiC, used in an SiC device.
2. Description of the Related Art
Application of silicon carbide (SiC) to a radiofrequency power device, a high-temperature device and an optoelectronic device has been expected and research toward practical application of silicon carbide (SiC) has advanced. A combination (TiAl) of titanium (Ti) and aluminum (Al) is generally used as a p-electrode for SiC device, that is, an ohmic electrode for p-type SiC (see Patent Document 1 and so on).
[Patent Document 1]
Unexamined Japanese Patent Publication No. Hei-5-13812
Generally, in most cases, a device needs an ohmic electrode. In a device using compound semiconductor, it is however generally impossible to obtain an ohmic junction between a semiconductor material layer and an electrode without any heat treatment, that is, Schottky characteristic appears when a metal layer is formed simply. On the other hand, in an ohmic junction based on a heat treatment, obtained contact resistance varies largely according to the semiconductor material, the electrode material, the heat-treatment temperature, the heat-treatment time, and so on.
At present, Ti/Al expected as an ohmic contact material having low resistance to p-type SiC needs to contain a large amount of Al for reducing resistance and needs to be heat-treated at a temperature of about 1000° C. though considerable reduction in resistance can be achieved by Ti/Al. A problem of reduction in device function and device life caused by deterioration of surface morphology and thermal damage to semiconductor crystal layers has been pointed out.